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From "Karthik Ranganathan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2231) Compaction events should be written to HLog
Date Thu, 18 Feb 2010 17:08:27 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2231?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12835290#action_12835290
] 

Karthik Ranganathan commented on HBASE-2231:
--------------------------------------------

Just wanted to attach evidence to the issue pointed out by Todd - "the regionserver also rolls
its HLog right after the pause. In this case, the master might not catch the rolled HLog file,
and the RS wouldn't be properly interrupted"

>From an email exchange between a few of us:

> Look at these snippets from the log:
> 2010-02-15 16:23:56,493 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: Got
ZooKeeper event, state: Disconnected, type: None, path: null
> 2010-02-15 16:23:57,848 WARN org.apache.hadoop.hbase.regionserver.HLog: IPC Server handler
30 on 60020 took 1200ms appending an edit to hlog; editcount=121
> 2010-02-15 16:24:04,697 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: Got
ZooKeeper event, state: Expired, type: None, path: null
> 2010-02-15 16:24:04,697 WARN org.apache.zookeeper.ClientCnxn: Exception closing session
0x326c5173bc80000 to sun.nio.ch.SelectionKeyImpl@5534afcb
>
> This means master did not take possession of the latest hlog. So the RS actually appended
into the log AFTER the zk timeout happened. The suggestion from yesterday's discussion (first
open the last hlog) should take care of this edit.


> Compaction events should be written to HLog
> -------------------------------------------
>
>                 Key: HBASE-2231
>                 URL: https://issues.apache.org/jira/browse/HBASE-2231
>             Project: Hadoop HBase
>          Issue Type: Improvement
>          Components: regionserver
>            Reporter: Todd Lipcon
>
> The sequence for a compaction should look like this:
> # Compact region to "new" files
> # Write a "Compacted Region" entry to the HLog
> # Delete "old" files
> This deals with a case where the RS has paused between step 1 and 2 and the regions have
since been reassigned.

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